Open reduction and internal fixation of posterior wall fractures of the acetabulum

The results of 94 patients with posterior wall fractures of the acetabulum associated with hip instability treated within 3 weeks of injury by open reduction and internal fixation were reviewed. Patients were followed up for an average of 3.5 years (range, 1-13 years). Fracture reductions were graded as anatomic (0-1 mm displacement) in 92 patients and imperfect (2-3 mm displacement) in two patients, as determined by plain radiography. However, postoperative computed tomography scans obtained in 59 patients revealed incongruency of more than 2 mm in six patients and fracture gaps of 2 mm or more in 44 patients. Complications included deep wound infection (one patient), deep vein thrombosis, (seven patients), and revision surgery to redirect an errant screw (one patient). Clinical outcome was graded as excellent in 34 patients (36%), good in 49 (52%), fair in two (2%), and poor in nine (10%). Radiographic results were excellent in 79 hips (84%), good in four (4%), fair in two (2%), and poor in nine (10%). There was a strong association between clinical outcome and radiographic grade. Variables identified as risk factors for an unsatisfactory result included age greater than 55 years, a delay greater than 24 hours from the time of injury for reduction of a hip dislocation, a residual fracture gap greater than 1 cm, and severe intraarticular comminution. The apparent disparity between the accuracy of surgical fracture reduction, as determined by plain radiographs obtained postoperatively, and clinical outcome is explained only partially by the limitations of plain radiography. Other variables are involved, many of which are under the surgeon's control but some are not. As is the case with other acetabular fracture types, the best results are predicated on anatomic fracture reduction.